The present invention relates to controlling vibration in surfaces and in particular relates to a system for controlling and/or damping vibration of dynamic surfaces.
In many industries, such as paper making, food processing, and textiles, or any other industry that processes a web of material, rolls are used for various processing functions, and in many instances, the stability of the roll is very important. For example, in a paper making assembly, roll vibration may cause variations in the thickness of the product being produced. Thus, it is desirable for the rolls to be as stable as possible and devoid of any imperfections, deflections or variations so that the paper being formed will be smooth and uniform. In addition to resulting in the production of inferior products, roll vibration may also result in damage to the roll itself or the machinery containing the roll. Thus, various attempts have been made to control vibration of rolls so as to avoid these problems.
One response to this problem has been to lower the rotational speed of the rolls in order to avoid or correct vibration-induced defects.
U.S. Pat. No. 5,961,899 to Rossetti et al. discloses a vibration control apparatus for processing a calendered medium that controls vibration between two or more rolls by controlling vibration induced thickness variations in a medium exiting from a nip. The apparatus includes a frame, first and second rolls relative to the frame and a force generator, such as an electromechanical active actuator, a servo-hydraulic actuator, a controllable semi-damper, and Active Vibration Absorber (AVA), or an Adaptive Tune Vibration Absorber (ATVA), providing canceling forces to control vibration between the first and second rolls, thereby controlling vibration induced thickness variations in the calendered medium. In certain preferred embodiments, the apparatus includes at least one sensor for providing a signal indicating a vibration condition of at least one of the first and second rolls, and a digital controller for controlling the signal representative of the vibration condition according to a feed-forward-control and providing a control signal to a force generator. Vertical and/or lateral vibration of the rolls may thus be controlled simultaneously. In addition, fundamental vibrational frequencies and their harmonics may be controlled individually, or in combination.
U.S. Pat. No. 5,447,001 to Nishimura et al. discloses a vibration control device for buildings. In one preferred embodiment, a building has mounted on its roof a hollow concrete-steel first mast carried on damping rubber supports. Within the hollow of the first mast, a second mast is mounted on anti-friction rollers, which roll on a low coefficient of friction interior floor of the first mast. The first and second masses are interconnected with a single element to vibrate these masses with a period of vibration that can be synchronized with the vibration period of the building to attenuate building vibration.
U.S. Pat. No. 5,403,447 to Jarvinen et al discloses a system in a press section of a paper machine for monitoring and controlling the running of a press felt. The press felts are guided by rolls having axial directions that are altered by means of an actuator so as to control the running of the press felts. The system includes detector devices for detecting one or more alignment stripes on the felts and oscillation detectors for detecting oscillation of the press rolls. The system also includes a microprocessor base controller for monitoring signals fed to the controller from the detectors. The controller analyzes the detector data in order to detect any felt-induced oscillations. The control system then generates signals for regulating the actuators of the guide roll that guide the running of the felts so that when the oscillation levels of the press rolls rise above certain limits, the direction of the guide roll on the felt that causes the oscillation is turned until an acceptable level of oscillation and/or a level of oscillation is reached.
U.S. Pat. No. 4,902,384 to Anstotz et al. discloses a wet press having vibration control. In one preferred embodiment, a wet press of a papermaking machine includes a pair of rolls defining a roll gap through which the paper being treated passes. The felt is guided in a closed loop path by additional rolls, which include a tightening roll. The tightening roll can be tilted to reduce roll vibrations by tightening the felt to set vibratory marks formed in the felt at an angle relative to the transverse width of the felt and the roll gap. A controllable positioning device is provided which includes a motor operated by a controller to automatically vary the tilt angle in response to sensed vibrations.
Vibration is also a problem when using a wet press of a papermaking machine. In such wet presses, as the felt and paper web to be drained are simultaneously conducted through a roll gap, water is pressed out of the paper web and transferred onto the felt web. The absorbed water is removed from the felt at another point along its closed loop path by, for example, a suction roll. The pairs of rolls forming the roll gap, along with their guides which engaged roll journals and the elastically resilient felt, form a vibrating system with a large number of resonance vibrations that can be excited during operation of the web press.
U.S. Pat. No. 5,785,636 to Bonander discloses a roll having an outer surface made of a fabricated fiber matrix for strengthening and reinforcing the roll to maximize roll stability.
U.S. Pat. No. 4,301,582 to Riihinen discloses a system that removes deflections from a roll using magnetic forces. The roll has a non-rotating axle with ends having a load imposed thereat and a cylindrical shell rotatably supported by bearings on the axle. A magnetic core is formed in the axle and a plurality of pole shoes are spaced from the shell by an air gap. A plurality of electromagnetic windings, each wound on the core at one of the pole shoes, produce a magnetic compensating force field between the shell and the core for responding to deflections in the roll.
U.S. Pat. No. 4,357,743 to Hefter, et al., discloses a controlled deflection roll having a roll shell which is radially movable in at least one plane in relation to a roll support. Position feelers or sensors are arranged at the ends of the roll shell for detecting one or more deflections in the roll shell as a function of deviations from a predetermined reference or set point. The position feelers control regulators operatively associated with pressure or support elements positioned between the roll support and the roll shell so that the roll shell is maintained in the reference or set position.
U.S. Pat. No. 4,062,097 to Riinhinen discloses a roll having magnetic deflection compensation that may be used in the calender or press section of a paper machine. The roll has an inner non-rotating axle and an outer shell surrounding and rotatable with respect to the axle, the axle and the shell having a common axis. The axle includes an inner magnetic structure while the shell includes an outer magnetic structure that rotates together with the shell. These inner and outer magnetic structures cooperate to provide attraction between the shell and axle on one side of the above axis and repulsion between the shell and axle on the opposite side of the axis, thereby achieving deflection control and/or compensation.
Other techniques used to reduce the detrimental effects of roll vibration include running process machinery at slower speeds in order to avoid resonance problems, and using back-up roll systems to reduce vibration.
Therefore, there is a need to have a vibration control system for a dynamic surface that damps or eliminates vibrations in the dynamic surface. There is also a need for a vibration control system that enables vibrations to be induced into a dynamic surface for any purpose necessary.